Conventionally, a printed wiring board in which a solder resist pattern which is a patterned solder resist film is formed on a substrate having a wiring provided on its top face is widely used. As electronic devices become smaller and densified, a still finer solder resist pattern is demanded in a printed wiring board.
As a method for forming a fine solder resist pattern, a method of applying a composition for solder resist by an inkjet method is proposed. In the inkjet method, the number of steps is reduced in comparison with the case of forming a solder resist pattern by a screen printing method. Therefore, in the inkjet method, it is possible to form a solder resist pattern easily and efficiently.
In the case of applying a composition for solder resist by an inkjet method, the composition is required to have a somewhat low viscosity at the time of application.
A composition for solder resist that is applicable by an inkjet method is disclosed in Patent Document 1 recited below. Patent Document 1 discloses a curable composition for inkjet containing a monomer having a (meth)acryloyl group and a heat curable functional group, a photoreactive diluent having a weight average molecular weight of 700 or less, and a photopolymerization initiator. The viscosity at 25° C. of the curable composition for inkjet is 150 mPa·s or less.